With accent marks:
Кто о чём, а вши́вый о ба́не.
Who is talking about what, and a lousy one about the bath.
This saying describes a situation when in a conversation of several people, one of them always talks only about what worries him. Even if the discussion is about a completely different thing. In the saying, such a person is compared to a "lousy one talking about the bath". Because until he bathes, and until this does not ease his suffering from the lice biting him, he will not care about anything else.
You can use this saying when someone always falls back on talking about the same thing.
Other Russian proverbs
The eyes are scared, but the hands are doing.
Repetition is the mother of learning.
They do not seek good from good.
Оne can not see the wood for the trees.
All is well that ends well.
Forewarned is forearmed.
Strike the iron while it's hot.
Being a guest is good, but being at home is better.